The present invention relates to devices for atomizing liquids and, more particularly, to devices for producing finely divided aerosols having uniformly sized droplets.
Finely divided aerosols have generally been produced by nebulizers employing compressed air to atomize fluids. These devices operate by allowing compressed air to escape from a small orifice at the end of a tube at high velocity. The low pressure created in the exit region as a result of the Bernoulli effect causes the fluid to be atomized to be drawn out of a second tube as a thin filament which is broken up into droplets of various small sizes, thereby forming a spray, as it is accelerated in the airstream. This spray is then directed around an impaction surface on which the large droplets are preferentially deposited, and whereby some uniformity is provided with respect to droplet size. However, most nebulizers operating with compressed air have difficulty producing aerosols having particle sizes approaching one micrometer, and cannot ordinarily generate aerosols which are sufficiently uniform in size so as to be "monodispersed".
Finely divided aerosols are highly useful in many applications and particularly in administering medications which are pneumonically delivered to the patient by inhalation. Most "inhalators" used in dispensing medications are compressed air nebulizers of sufficiently small size to be suitable for hand-held use. However, in view of the characteristic limitations of such nebulizers and the further limitations inherent in the small size of most inhalators, users of these devices have had great difficulty in providing aerosols having uniform particle size, and in the related problem of providing consistent measured amounts of medication.
Difficulties include the use of environmentally harmful propellants that may affect the earth's atmospheric ozone layer. Other difficulties include formation of large droplets and streams that cause liquid to impact tissue membranes of the mouth and throat rather than form a mist that is airborne into the furthest reaches of the lung.
It is therefore an object of the present invention to provide a portable nebulizer capable of generating finely divided aerosols which are substantially monodispersed.
It is another object of the present invention to provide a nebulizer which may be small enough for hand-held use and yet provides aerosols of substantially uniform particle size while being capable of supplying medication in consistently measured dosages.
It is a further object of the present invention to provide a nebulizer which may be powered by the hand-gripping pressure of a user of the device and which is sufficiently economical to construct so as to be disposable.